How Accurate Are Apple Watch Calories? How to Make Them as Accurate as Possible

Apple Watch calorie calculations are based on health standards, and are known to be accurate. Still, there are things you can do to ensure your watch’s calorie calculations are as accurate as possible.

If you are athletic or active, you may be asking "how accurate are Apple Watch calories?" I was personally surprised to learn how accurate they really are. This article discusses how reliable the calorie calculation is on your Apple Watch, as well as how to improve your Apple Watch calorie accuracy.

Related: Active Calories vs. Total Calories on Apple Watch: What’s the Difference?

What's in This Article:

How Does Apple Watch Calculate Calories? 

Apple Watch tracks your heart rate and movement, and uses your personal health information such as height and weight to track your daily calorie expenditure.

The calorie tracker is based on a scientific principle called the metabolic rate. Metabolic rate is the rate of a person’s metabolism, or how quickly the body expends the calories ingested through food intake.

Each individual has a unique metabolic rate, but scientists can accurately predict an individual’s metabolic rate based on their gender, weight, and height.

When you set up your Apple Watch, you give Apple this info in the Health app. It then uses this personal information to calculate your Basal Metabolic Rate (BMR), which is your metabolic rate under normal resting conditions, and your Active Metabolic Rate (AMR), which is your metabolic rate while you are exercising. Apple Watch uses your heart rate and movement to detect increases or decreases in activity, which measures AMR. 

The Apple Health app determines how much the average person of your size, age, and gender needs to exercise in order to run a calorie deficit. Meaning, how much you need to move and be active to burn more than the amount of calories you consume in a day.

 What Are Active Calories on Apple Watch?

Calories are burned in two ways: through your body maintaining itself at rest, and through additional calories used during exercise. These additional calories used during exercise are what Apple calls Active Calories. Total Calories is equal to Active Calories plus BMR, or the sum total of calories burnt at rest and calories burnt during exercise. You'll know you've reached your personal goal of Active Calories burned by looking at your Apple Watch activity rings: When your red Move ring is closed, you've hit your Apple Watch Move goal.

How Accurate Is Apple Watch Calorie Tracking?

This question can be asked and answered in two parts.

First, how accurate is Apple's measurement of BMR, the calories used as determined by your age, gender, and size? The answer is that this calculation is pretty accurate. BMR science is commonly used in the medical field, and the indicators used by Apple in making this calculation are industry-standard.

Next, how accurate is Apple's calorie expenditure tracking? A study conducted in 2017 by Stanford University found Apple Watch to be the best in its class out of 60 other competitors for energy expenditure tracking, with the best heart rate tracking and top movement tracking.

While a medical device such as a calorimeter may be better at tracking calories used, the Apple Watch is about as good as you can get for accuracy and ease of use in a compact device. It is crucial, however, that your watch is set up correctly to ensure that calories are tracked as precisely as possible.

How to Improve Calorie Tracking Accuracy on Apple Watch 

Because calorie usage depends so much on your own biology, it's essential that your Apple Watch is updated with the latest information regarding your weight, height, and activity. This can be done in the Health app. This Health app information is also key to tracking your exercise minutes correctly when using your Apple Watch, so keeping it updated is a good habit to get into.

  1. Open the Health app.

    Open the Health app
  2. Select Show All Health Data.

    Select Show All Health Data
  3. Scroll down until you see Height and Weight, and select the category that needs to be updated.

    Select a category to update (height or weight)
  4. Select Add Data and input your new height or weight.

    Tap Add Data in the upper-right corner

You will also want to ensure that your watch is not too loose to allow the heart rate monitor to accurately track your heartbeat. Also ensure that when you exercise, you select the activity from the Workout app on your Apple Watch that most closely matches the exercise you are performing to allow Apple Watch to accurately track your movement.

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Author Details

Erin MacPherson's picture

Author Details

Erin MacPherson

Erin is a Web Editor for iPhone Life and has been a writer, editor, and researcher for many years. She has a degree in communication with an emphasis on psychology and communication, and has spent many of her professional years as a coach in various business and specialty fields. Erin officially joined the ranks of iPhone and Apple users everywhere around nine years ago, and has since enjoyed the unique and customized feel of Apple technology and its many gadgets. When she’s not working, Erin and her son enjoy outdoor adventures, camping, and spending time with their eclectic collection of pets.